MadSci Network: Physics |
Seriously, the reason for the separation of matter is the electrostatic force. The electron cloud of atoms repel each other. Electrons in atoms should not be viewed as particles but as waves that occupy space. The electron clouds are usually, very resistant to change of shape. So when your head bangs into the wall, the hardness of your head and of the wall are determined by the bonding arrangement (electrons again) of each material.
Another way to think of it is to envision matter (on some scale) as a window screen. Dust and bugs might be able to get through the openings but bigger stuff like people or other screens cannot pass through.
Hope this helps,
Tom Cull
Try the links in the MadSci Library for more information on Physics.